REPORT OF THE CHEMIST. 



287 



Analyses of butter. 



ESTIMATION OF FAT IN MILK. 



The percentage of fat in milk is one of the best indications of the 

 presence or absence of added water. Various methods of speedily 

 and accurately estimating the percentage of fat have been proposed. 

 One of the most successful of these is known as Soxhlet's areometric 

 method. The principle of this method is based on the fact that if the 

 milk first be rendered slightly alkaline and then shaken with ether 

 the fat passes into solution, and when the mixture is allowed to rest 

 for some time the etherial solution of the fat will collect at the top. 

 The specific gravity of this solution will vary according to the con- 

 tent of fat which it contains, and by the determination of this specific 

 gravity the percentage of fat is determined. 



The great objection to the use of this method is found in the diffi- 

 culty with which the ethereal fat solution separates. Various theo- 

 ries have been proposed to account for this peculiarity of milk in 

 refusing to allow the ether solution to separate. Caldwell and Parr 

 have supposed it to be due to the bran in the cow's food; Liebermann 

 ascribes it to failure of manipulation; Schmoeger, that it is caused by 

 the milk standing on ice; Soxhlet thinks it is the result of deficiency of 

 fat; and others attribute it to differences in age and breed of the cows. 



Therefore the method, in order to be of general application, must 

 be subjected to some radical modification. In this direction were the 

 attempts to secure a more prompt separation by varying the amounts 

 of caustic potash solution emi)loyed. These attempts, as the record 



